Thea Alvin is pictured with one of her creations at the Dharma Door retreat center in Underhill.

MORRISVILLE — On May 17, the price of an act of wonder went up 2.3 percent. Stonemason Thea Alvin had been asking $44 an hour for her extraordinary labors. After that Friday, her birthday, the same job would cost $45.

“I typically work for my age in wages,” Alvin said. “It’s a rule I invented.”

The business of building a 50-ton stone helix on the front lawn is perhaps the definition of a specialty trade. Almost no one other than Alvin has the imagination and skill to do it.

And her life’s training would be particularly hard to emulate. Alvin grew up in a commune (which, on second thought, might have been a cult), partied with the Grateful Dead when she was 5, spent the better part of a school year in her bedroom under a kind of “solitary confinement” and eloped at 18 and raised three children in a cabin with no running water.

The experience has left her with a creative disposition and an underdeveloped interest in capitalism.

“Because my lifestyle is so low-budget, I don’t need to do a lot of work for a lot of money,” Alvin said. She made a patio and a fire pit at her dentist’s home in exchange for a new tooth. “I barter for food all the time,” she added.

Alvin does a lot for her friends in the neighborhood, the scruffy little hamlets that ring the well-groomed ski principality of Stowe. On a recent Thursday morning, she offered a driving tour of her ambit.

One of the first stops was a yak farm where she had rehabbed a retaining wall below the barn. Across from the state Capitol in Montpelier, a little ways down the road, she had installed a 12-ton mound of environmental art. This was a meditation in slate on the power of storms and floods.

One job was as good as the other. Wherever you set it, a stone is a stone.

To the extent that her craft involves breaking rocks in the hot sun, Alvin appears to be having fun. She wields a 4-pound maul that she calls Garfield. “It’s short and fat,” she said, “and really likes lasagna.”

She admits to having a “hammer fetish”: She owns three to four dozen, all of them named. “I have a 7-pound hammer that you hold in one hand, and that’s called Bam Bam,” she said. “And I have a 12-pound maul, and that’s called the Convincer.”

She rarely strains her back hoisting these tools. For starters, she doesn’t have much of a back to strain. She stands an inch or two over 5 feet, and that’s in her work Crocs.

One of her longtime friends, Suzanne White, recalls lending a hand on a stone job. “She asked me to pick up one end of a big stone,” White said. “And I couldn’t move it. So she just lifted it by herself.”

Alvin reckons, “I top out at around 150 pounds. I can move a rock that’s 200 pounds, but I can’t pick it up.”

Still, once you have the stones, anything is possible.

It is feasible to bully a single boulder, but the better part of the art is persuasion. Stacking stones, Alvin said, “is like playing Tetris with real objects.”

The building form is universal, said Norman Haddow, a 75-year-old master craftsman in the Dry Stone Walling Association of Britain. “Anywhere there’s a little bit of farming and you want more land, you clear it to get the stones off it,” he said. Turning this material into a wall keeps the crops on one side and the “wild animals” on the other, which is a pretty good definition of civilization.

Haddow lives and works in Scotland, at the edge of the Highlands, and he has seen Viking-era walls nearby, where “the stone is built exactly the same way I do it.” Almost as longstanding, perhaps, is the Old World schism between dry “wallers” (that is, farmers) and mortar-smearing “masons” (tradesfolk). “Masons shape the stone,” he said, “and wallers find the right one.”

Most Americans take a less dogmatic view, and Alvin works in both idioms. But as Haddow said, “she seems to have the knack to find the right stone.” He was calling from Alton, Ontario, where he makes an annual pilgrimage to play around at a dry stone festival in Canada (formerly known as Rocktoberfest). That’s where he first encountered Alvin’s stonework.

“By my standard, it’s impeccable,” he said. Yet to Haddow’s expert eye, “she’s an artist rather than a waller.” This is in keeping with the migration of the form from the sheep pasture to the manor lawn. “People like Thea are doing features for rich people,” he said.

It’s certainly not practicality that inspired a European business magnate to commission a primitive stone chapel and a medieval walled garden for his hillside Vermont vacation home. The secret garden (overseen by Irene Facciolo, an architect, and her Thunder Mill Design) is a folly, to be sure.

Alvin fashioned brick patches for the high walls, to mimic centuries of weathering, and hand-carved the fountain out of autoclaved aerated concrete, which is not even vaguely authentic to the Plantagenet period.

But there’s no way to fake the look of 460 tons of stone. It’s a real wall and a real sanctum that Alvin has built. And the price tag — $100,000 for the masonry and more than $500,000 overall — wasn’t funny money, either. (The job stretched over three summers, and by the time she was done, Alvin figured she probably pocketed no more than $10,000.)

Alvin has placed a more-public calling card in her own front yard, hard against Route 100. It’s a 6½-foot-high helix made of fieldstone, without a dab of mortar (or “the devil’s cream,” as she calls it) to suspend the loops in the air.

This sculpture, too, contains an element of trickery. The top part of the spiral is a simple arch. It’s the bottom half of the stone circle that curves sinuously, creating the impression of a stretched-out Slinky. Passers-by will veer off into her dirt driveway, Alvin said, and ask questions like: “Does it have steel rods in it? How many people does it take to hold it up as I make it?”

The answers are no and none. Alvin shapes the stones and fits them around a wood form, each pointing toward the center. Then she knocks out this hoop, leaving an uncanny stone span. The geometry works, but so does the illusion.

There is nothing precarious about the helix. You can push on it. Left alone, Alvin’s rock piles could remain standing for millennia, she said.

But today’s stone is spendy: The good, hard stuff costs $200 or $250 a ton in Vermont. That’s about the right amount to stack a 3-foot-long segment of wall, 30 inches high and 18 inches deep. No one would mistake it for Machu Picchu.

The upshot is that Alvin is constantly cannibalizing rock from one mound to feed another. She teaches a stone workshop at Yestermorrow, the neighborhood’s bohemian building school, and summer after summer, her students dismantle and reassemble the same sculpture, most recently what she termed “a Venus Gate.” This is a stone monument whose aperture evokes what might discreetly be called womanhood.

“The beautiful thing for me about dry stone masonry, and my life’s work, is if you want to change it, you just change it,” Alvin said. “There’s nothing permanent about this at all.”

The day before Alvin’s birthday party, another transition was under way. A couple of housemates were loading up a Subaru and heading west: One was joining a wolverine research project in Montana; another was boarding a fishing trawler in Alaska. Alvin’s residence comprises eight bedrooms and two kitchens, and there’s no point in trying to keep track of all the comings and goings.

By her estimation, the house’s stone foundation dates back to 1810. The original dwelling has been added on to and the additions have been added on to, she said, and as a result the “floors and ceilings and walls go in all different directions.”

In 2000, she bought the roost with a beau for $158,000, intending to create a kind of artists’ kibbutz. When the boyfriend joined the parade of departures, she bought the house a second time, with a friend. The bank was pickier this time. To secure a loan, she removed a supernumerary third kitchen and built a greenhouse and studio connecting two separate sleeping zones. The result, she said, is “like a hamster habitat with a tunnel and tower.”

But now she is free to do whatever she likes with the property, and she does. For a time, the 2-acre garden and pasture contained a shed made entirely of doors. The structure was a visual pun, she said: One door opens and another closes.

It seems significant, then, that her love of two years, a 37-year-old carpenter and sculptor named Michael Clookey, recently knocked down the doors and replaced them with a pergola.

Still, he hasn’t touched the old cruiser bikes that hang from a butternut tree above the goat-and-chicken pen, which is a flight of fancy any way you look at it.

At this point, one of her off-and-on boarders, a 24-year-old photographer and part-time barista, walked into the dining room. After returning from a romantic misadventure in Virginia, she had been living in the garret of the unheated attic, which she reaches on a jerry-built ladder.

“That’s Robyn, my daughter,” Alvin said.

Alvin lost custody of the children in their early adolescence, after splitting with her husband. And although the two girls ultimately settled in with her (Aimee, 22, is a chef), her son “lives in a town 5 miles from here,” she said, “and I haven’t seen his face in five years.”

This estrangement has proved a painful re-enactment of her childhood. Alvin’s father was a teenage arsonist and an alumnus of reform school and state prison; her mother was a budding hippie and idealist. As a couple, they did not complete each other.

With Alvin in tow, her mom wandered off to western Massachusetts and a commune called the Brotherhood of the Spirit, founded in a treehouse. Devotees surrendered their paychecks to support the leader’s psychedelic rock band, Spirit in Flesh. After a year or two, the family fled at night in a stolen car.

And yet Alvin was no closer to a conventional childhood. When she and her sister contracted the mumps, Jerry Garcia of the Grateful Dead wrapped their faces in raw bacon as a folk remedy.

Alvin’s mother, Abbie, disputed this recollection — but only a little. She enjoyed a brief relationship with the Dead’s lyricist, Robert Hunter, she said, although she declined to categorize it, except to say that it was too short. And he was the one who proposed the bacon. “I tried it on them and they hated it,” she said from her home in New Bedford, Mass. A prescription from the doctor worked better. “It goes to show you how gullible I was. I was doing LSD at the time.”

The ’70s, as a whole, were strange: It was a time, Abbie Alvin said, when a caring mother could be sucked into a vortex of misfortune.

“She was stoned a lot, and I was hungry a lot,” the younger Alvin recalled.

By comparison, her father’s household appeared rich. “I thought I’d give it a try,” she said.

A judge granted custody to her father, David Duarte, and Thea Alvin moved into the family’s old barn on a cranberry bog in Martha’s Vineyard. He had joined a Jehovah’s Witnesses congregation, and the mood of the household had changed. Alvin was zealous herself for a time.

But there were teenage troubles in the form of a Nissan Maxima wrecked at 80 mph, and some fast times with a boyfriend. The church “disfellowshipped” the young couple, Duarte said — a kind of shunning. And Alvin spent almost a year banished to her bedroom: Rapunzel in her tower.

“Between November and June, I did no schoolwork,” Alvin said. “I read a dictionary and I read the Bible.”

When she was 18, she said, “I ran away with the boy I had slept with. We got married immediately.” This was the start of another exile, living in a shack without power or plumbing while raising three young children.

Duarte said that he brought his daughter yearly checks of $5,000 from her grandmother. “I was glad to do it,” he said.

Alvin said, “I never received any money.”

Nonetheless, she took something away from the years with her father. “He was a mason,” she said, and “the summer I was 16, I went to work.”

They built chimneys and fireplaces. “I had to hand-mix the mortar and carry bricks in a rack,” Alvin said. A rack held nine bricks, and each brick weighed 4 pounds. “I’d bring two racks of bricks to him at a time,” she said, a 72-pound load.

Her father could lay the bricks as fast as she supplied them. “I learned how to work,” Alvin said. “I learned not to show you’re tired or weak or upset.”

And one more thing: “I learned how to mix mortar really well.”

Alvin has yet to reach rock-star status, but you wouldn’t know it from her touring schedule. She is one of those people who will say something like, “I was living in China studying calligraphy in pagodas,” and then somehow end the paragraph amid medieval stone ruins north of Milan.

In late April and May, she visited Illinois to lead a stone workshop, then flew to Belgium to fabricate a pizza oven, after calling on St. Croix, in the Caribbean, where she is remodeling a kitchen for the wife of a Napoleonic War re-enactor.

This latest odyssey will end next week at the Village Laboratory, a 15th-century Italian site called Ghesc that has been abandoned for a century and overtaken by forest. “The chestnut trees are inside the houses,” she said. In concert with Italian masons and architects, Alvin brings Yestermorrow students to help restore individual houses.

She pulled out an Italian book on the experimental site and pointed to a set of architectural sketches. “I’ve begun the purchase of one of the houses,” she said. Then she corrected herself: “It’s literally just a pile of rocks.”

Many of the ruins have been owned by the same families for generations, or maybe centuries, and trying to arrange a sale is a byzantine affair. (Alvin’s family seems functional by comparison.) She imagines her friends and students and children coming to live in the village for a few months at a time.

The page was falling out of the book by now. Imagine an orangery in front of the remnant pillars. “In my vision,” she said, “this wall is here, and this wall is there.”

The odds favored oblivion. But then, maybe Alvin will be able to piece the home together again. Nothing is ever set in stone.

“The beautiful thing for me about dry stone masonry, and my life’s work, is if you want to change it, you just change it. There’s nothing permanent about this at all.”